BACKGROUND AND OBJECTIVES: Firefighters face serious risks to their health and safety in the performance of their duties. In addition to the diverse occupational hazards well-known to the public, firefighters are also occasionally exposed to high levels of noise, such as sirens, horns, and electronic alerting signals. MATERIALS AND METHODS: We first measured the noise emitted by two fire trucks and one ambulance. Next, we enrolled 171 firefighters (164 males, seven females). We designated the employees of a private school as controls for the firefighter group. After selecting workers, including audiometric testing at 1,000 and 4,000 Hz, the groups were age- and gender-matched. Both groups were included separately for the right and left ears at pure-tone test frequencies at 1,000 and 4,000 Hz. We chose the better ear thresholds and analyzed the differences in hearing levels at each frequency and each age group between the firefighters and controls. RESULTS: The sound pressure levels of the siren in and out of an ambulance, the first fire truck, and the second fire truck were 99.3 dB (A) and 108.9 dB (A), 92.3 dB (A) and 108.3, and 78.8 dB (A) and 99.0 dB (A), respectively. At 4,000 Hz, the hearing threshold was significantly increased by work period (p<0.01). Each hearing threshold level was significantly higher than controls (p<0.01). CONCLUSIONS: Many of the noise sources produce sounds exceeding 90 dB (A), and some firefighters may be exposed for brief periods to levels that exceed 105-110 dB (A). The hearing threshold level in firefighters is higher than the general population and noise-induced hearing loss in firefighters is possible. In the future, consistent, effective, and long-standing implementation of hearing conservation programs are needed, and special health examinations for hearing levels in firefighters must be conducted.